1. Field of the Invention
This invention relates to a method of bleaching textile materials using potassium based bleaching liquors, both containing hydrogen peroxide and water. One liquor contains commercially available potassium orthosilicate, the other liquor contains the products of the reaction of potassium hydroxide and sodium silicate in such relative concentrations that the final liquor contains more potassium than sodium ions.
In the manufacture of cellulose fibers into a marketable product, either the fibers or the produce made from the fibers is often bleached to improve its appearance and make it more receptive to other manufacturing processes. Such bleaching is done with various oxidizing or reducing agents, an aqueous alkaline solution of hydrogen peroxide being presently the most successful and accepted method. Alkaline hydrogen peroxide solutions generally are not stable. Their decomposition rate must be controlled in any bleaching process in order to achieve desired results; it is known to use sodium silicate for this purpose. However, the use of sodium silicate per se has a number of disadvantages in most bleaching processes, manifesting themselves in the decomposition of insoluble calcium and magnesium silicate products on the equipment and on the goods being processed. Because of these problems, the textile industry has been looking for a cheap, relatively easy-to-handle composition that would achieve the desired bleaching results obtained using sodium silicate (water glass) and hydrogen peroxide without the undesirable deposition of insoluble calcium and magnesium silicate products.
2. Description of Prior Art
U.S. Pat. Nos. 2,927,082; 3,951,594; 3,150,918 and 3,353,093 are illustrative of the prior art relating to bleaching of textile cellulosic fibers and/or goods using a mixture of sodium silicate and hydrogen peroxide. The first-mentioned patent employs a magnesium salt, such as Epsom salt and magnesium-glyconate, whereas the second-mentioned patent discloses the use of sodium orthosilicate in combination with hydrogen peroxide and magnesium-polyphosphate stabilizers. Both of the last two mentioned patents teach a textile bleach liquor containing hydrogen peroxide, sodium silicate and caustic potash; however, the concentration of caustic potash is too small to achieve potassium orthosilicate.